1. Field of the Invention
This invention relates to spectral-based data compression, and more particularly to the field of frequency-based data substitution for enhanced video compression rations.
2. Background of the Invention
Digital storage and/or transmission of video data has applications in entertainment, video conferencing, education, medicine, and virtually any application where moving pictures are desired. Video data requires large bandwidths whether the video data is to be stored, or transmitted over finite bandwidth transmission media such as modems and various other Internet connections. Various algorithms and systems exist for encoding and compressing video data, including the audio data that is normally included within the video data. One such standard is the Motion Pictures Expert Group (MPEG) standard which is the ISO/IEC 11172 standard entitled xe2x80x9cCoding of Moving Pictures and Associated Audio For Digital Storage Media At Up To About 1.5 Mbit/s.xe2x80x9d However, 1.5 Mbit/s is too high a digital data rate to enable real time video playback over Internet connections, even including digital subscriber line (DSL) connections. Accordingly, a need exists for improved techniques for compressing and encoding sensory stimulus data streams such as video data streams, audio data streams, or combined video/audio data streams.
In the invention, frequency information is selectively removed from a video signal. The removal of the frequency information includes reducing the magnitude of certain frequencies to zero. This magnitude reduction process can be thought of as color xe2x80x9craking.xe2x80x9d The color raking is performed periodically in the frequency spectrum. The removal of frequency information further includes oversaturation, which is the shifting of certain color values to nearby color values. The oversaturation process can be thought of as color rounding. Both the color raking and the color rounding is performed in portions of the visible spectrum in which the human eye will not noticeably perceive that video information has been lost, i.e., the image quality will not be visibly degraded. In this way the cardinal number of color values within the video signal is decreased. This reduces the number of colors values that a video data compressor needs within its color palette, thus reducing the computational load on the video compressor and reducing the bit rate required to support video image transmission and/or reproduction. That is, the compression ratios are increased. The invention therefore takes advantage of strengths and weaknesses in the ability of the rods and cones within the human eye to perceive colors of varying magnitudes and wavelengths.
The present invention also includes matching of a reduced spectrum lighting source with a reduced color palette within the data compressor. The use of the reduced spectrum lighting source allows the size of the color palette to be reduced without visible degradation in image quality, thus further enhancing the compression ratios. The present invention further includes filtering the video signal with a filter whose frequency response is generally the reverse of the human eye""s spectral response to the output of a video playback device such as a computer monitor.
The above-described features and other features and benefits of the present invention will become clear to those skilled in the art when read in conjunction with the following detailed description of a preferred illustrative embodiment and viewed in conjunction with the attached drawings and appended claims.